First-principles thermal equation of state of fcc iridium

TL;DR

This study derives the thermal equation of state for fcc iridium using first-principles molecular dynamics up to high temperature and pressure, comparing theoretical predictions with experimental shockwave data.

Contribution

It provides a comprehensive first-principles-based thermal EoS for fcc iridium, including key thermodynamic parameters and comparison with shockwave experiments.

Findings

Theoretical Hugoniot matches experimental data with some discrepancies.

Derived thermodynamic parameters align with experimental values.

Discrepancies suggest potential formation of new Ir phases under extreme conditions.

Abstract

The thermal equation of states for fcc iridium (Ir) is obtained from first-principles molecular dynamics up to 3000 K and 540 GPa. The equation of state (EoS) is globally fitted to a simplified free energy model and various parameters are derived. The theoretical principal Hugoniot is compared with shockwave experiments, where discrepancy suggests formation of new Ir phases. A few representative EoS parameters, such as bulk modulus $K_T$, thermal expansivity $\alpha$, Gr\"uneisen parameter $\gamma$, and constant pressure capacity $C_P$, Debye temperature, $\Theta_D$ are computed to compare with experimental data